The present invention relates to closures that provide a seal prior to their first use, and thereafter burst open to form a check valve to provide backflow protection.
A check valve is a type of valve that permits flow of a fluid in one direction while inhibiting reverse flow. Such valves are typically used to prevent contamination of plumbing systems. "Duckbilled" type check valves usually have a cylindrical base/inlet end that fits snugly into a conduit through which the fluid will be flowing. The outlet end of the valve tapers somewhat like the bill of a duck. There is a central bore extending through the valve between the entry and outlet. Normal fluid flow drives the flexible duckbill open and permits flow through the valve. Reverse flow drives the bill closed.
Prior art duckbilled check valves are available from many suppliers. Three such suppliers are Vernay Laboratories, Eagle-Picher and Moxness.
While duckbilled check valves have been used in a wide variety of applications, they are particularly well suited for use in nozzle assemblies that assist in dispensing actives (e.g. cleaners, fertilizers, herbicides, pesticides) from the end of a garden hose. See e.g. check valve 15 in U.S. Pat. No. 5,906,316. The disclosure of this patent and of all other publications referred to herein are incorporated by reference as if fully set forth herein.
Duckbilled check valves are typically made from elastomeric materials such as styrene-butadiene, nitrile, and silicone via compression molding. In such a process the valve is usually formed without the front bill slit. The bill is then cut to form the outlet at the "lips" of the bill in a secondary operation. This cutting step adds some cost and requires careful process control (which can slow the rate of production). Also, the resulting valve is designed to always permit flow from the inlet to the outlet end of the valve.
In U.S. Pat. No. 2,802,608 there was disclosed a closure that sealed various consumer products prior to first use. The closure was designed to be broken open prior to first use. However, the closure relied on external manual pressure to open it and to close it.
There is a need for improved ways of forming duckbilled check valves.